If you’ve just set the goal to start paying more attention to your diet plan and hope to shed a few excess pounds you’ve packed on over the last few weeks, months, or years, it’s time to get serious about calories.

When it boils right down to it, weight loss will very much depend on your calorie intake versus your calorie expenditure. Consume more calories than you burn off over the course of the day and weight gain is to be expected. On the flip side, if you burn off more calories than you consume, that is where the ‘weight loss magic’ takes place.

Your body is forced to turn to an alternative source of energy and that source is very often your body fat stores.

Now, while calories dictate which direction the scale moves, your macronutrient intake dictates which type of weight you gain or lose.

Let’s look at these concepts into greater detail so you can get the full picture of why managing calories and macros is so critical to your success.

Calories In Versus Calories Out

As just noted, the single most important factor determining your success is how many calories you consume. While you may find some diets out there that proclaim that calories don’t matter – all you need to do is eat healthy, don’t believe them. They are only going to lead you astray.

It’s the basic law of thermodynamics. Energy cannot be created or destroyed. If you consume energy, that energy either needs to be used up by your body through metabolic events or expended as energy. If it isn’t, it’s going to be stored. It doesn’t really matter if this energy is coming from carrots or cake. Excess energy is excess energy.

And likewise, if you aren’t eating enough energy to sustain all your day to day movements and your metabolic events, the body will be forced to find energy elsewhere. This energy comes from your tissue storage – notably, fat storage.

So the number one rule governing a successful weight loss program is:

Energy in < Energy out

If you can master this, you are one giant step ahead of the game.

This now begs the question, how many calories should you eat? .

If only it was a simple answer…

What you need to realize with this is that every single person will be different here. We all have different lifestyles and different bodies and therefore burn different amounts throughout the day. This is not a one-size-fits all answer, which is why using some cookie cutter diet program rarely works out.

You need to tailor your nutrition intake to your body.

Getting back to how many calories you eat, this will depend on three things:

Your basal resting metabolic rate (BMR)

The types of activities you are performing and their duration

Your overall food intake, also known as the thermic effect of food (TEF)

Let’s look at each of these closer.

BMR

First you have your basal metabolic rate. This refers to how many calories your body needs to simply sustain itself on an every day basis. It does not include any form of movement into the mix – it’s just the energy required to keep your brain functioning, your lungs taking in oxygen, your heart beating, your liver working, and so forth.

It’s your essential calorie needs.

While this number will vary from individual to individual, it is relatively static based on your total lean body mass. The more lean body mass you have, the more energy your body will require to stay alive. This is why those who are very well built and have a lot of muscle often can eat more food and stay lean. All that muscle is highly metabolically active, thus it drives their BMR values up.

One of the most basic ways of calculating your BMR value is to use the Harris Benedict equation. It is as follows:

Since men typically have more lean muscle mass than females do, this is why we see their BMR values higher for the same amount of body weight compared to women. As women have a higher level of essential fat (making up part of their body weight), their resting metabolic rate is lower.

Remember, fat mass requires very few calories to maintain itself, so it does nothing for improving your BMR values.

If you don’t feel like doing fancy calculations, you can usually get a rough estimate for your BMR by simply multiplying your body weight by 10 if you are a female or 11 if you are a male.

This will provide a good starting point upon which you can begin.

Activity Factors

Next you need to look at your activity level. What type of exercise are you doing and for how long?

Here again, this will vary greatly by the individual and even amongst the same individual on a day o day basis. Some days you’ll be far more active than other days, so this can impact things.

Since we’re looking at averages here though, you want to think about your general activity level. On the whole, how active are you? Do you exercise 1-3 times per week? 3-5 times per week? 6+ times per week? And how active is your lifestyle outside of exercise? The more you move, the more calories you burn, it’s that simple.

To help estimate this, we use what’s known as an activity multiplication factor. Listed below are these factors so you simply want to find where you stand and then multiply that number by your BMR value

One last thing that needs to be mentioned is that if you are doing intense interval training or weight lifting, you’ll actually experience an increase to your resting metabolic rate (BMR) values for up to 48 hours after the exercise is over. One study published in the Medicine and Science in Sports And Exercise journal noted that when subjects performed strength training activity, their overall RMR rate was increased by 7%. So with those activities, you aren’t just burning calories while you do the exercise, but for hours after as well.

Consider them to give you an added boost to your fat loss success.

Food Intake Factors (TEF)

Finally, the last thing you need to take into account is the food intake factors. This is basically the energy required to break down the food that you are eating on a daily basis.

Now, if you eat a general mixed diet with a fairly even amount of proteins, carbohydrates, and dietary fats, you’ll get a general TEF value of around 10%. This amount has already been worked into the Harris-Benedict equation above, so you don’t need to do anything further. It is good to know however that it does exist.

If, on the other hand, you are eating a diet higher in protein – which is often recommended for fat loss purposes, this can give you a slight boost over and beyond that 10%.

As protein requires more energy to break down and digest, it can give you a little extra added boost. You generally don’t really need to account for this so to speak, but just remember that if you are eating a bit more protein in your diet, it can be slightly helpful. Likewise, insoluble fiber is not fully digested by the body either as some will pass out through you, so theoretically, you won’t be netting the full 4 calories that each gram of fiber provides like that of a regular carbohydrate without fiber. Again, no need to account for it, but it’s helpful to know why these foods – protein and fiber rich foods – are weight loss winners.

Remember, since you are trying to lose weight, you now need to eat fewer calories than this. How much fewer depends on the speed of weight loss desired.

There are 3500 calories in one pound of body fat, so create a 500 calorie deficit per day (eat 500 below maintenance) and you’ll lose about one pound per week. Use a 250 calorie deficit and you’ll be sitting at half a pound per week.

You can go slightly higher – up to 750 calories if you have a lot of weight to lose, but avoid going much higher than this. For most people, an aggressive 1000 calorie day deficit will put them at risk for nutritional deficiencies and lack of energy.

How “Macros” Factor In

To see optimal results, you need the proper amount of each of these nutrients as each has a different role in the body. Miss out on one and your body may not burn stored fat as well and instead, could resort to burning lean muscle tissue. This is clearly unwanted as it will result in the decrease in your BMR value, reducing your daily calorie expenditure.

Let’s look at each macro briefly.

Proteins

Protein rich foods are the primary foods that supply the building blocks upon which body tissue is made from. These ‘amino acids’ as they’re called help repair muscle damage as well as help create new cells for the other areas of the body as well including your bones and organs.

Of all the nutrients to take in with your diet, protein is the most critical. When in a calorie reduced state, you need even more protein than normal as there is a higher chance your body may use some incoming protein as a fuel source since fewer carbs and fats are available. This in turn leaves less protein over for maintaining lean muscle mass.

You should generally be aiming to consume around 0.89 to 1.76 grams of protein per kilogram of body weight depending on your activity level according to the American Physiological Society. Good sources include tofu, tempeh, seitan, beans, lentils, legumes, nuts, seeds, and hemp protein powder.

Try and fit these into each meal and snack that you consume.

Carbohydrates

Next you have carbohydrates. This is the primary energy providing nutrient, so another you won’t want to miss out on. You do want to take your carbohydrate intake a little lower while on a fat loss diet however as this is what will help get your body turning to stored body fat as a fuel source.

The trick when selecting your carbohydrates is to choose ones that are not processed and instead, come straight from the ground. Rely primarily on fresh fruits and vegetables as these are lower calorie carbohydrate choices and place complex carbohydrates like oats, potatoes, rice, beans, and barley closer to your exercise sessions. This way, you are providing the high level of fuel when you need it most.

There are no set requirements for carbohydrates so you’ll find that this nutrient varies considerably based on your total calorie intake. The more calories you are eating in a day, the more total carbohydrates you can consume.

Dietary Fats

Finally, dietary fats are another must-have. Some people fear fat as they think that eating fat will cause them to gain fat, but this isn’t the case. While fat is more calorie dense than protein and carbs coming in at 9 calories per gram compared to four calories for the former two nutrients, you still do need it in your diet plan.

Dietary fats help to keep your hormones properly regulated and also help to ensure that you are getting the fat soluble vitamins that your body needs. Healthy dietary fats also help control your appetite level and keep blood sugar under control, so those are two additional reasons they are important as part of a well-balanced fat loss plan.

While there’s no set amount of dietary fats you need to consume like protein, you should generally aim to take in at least 0.3 grams/lb. of body weight. Consider this a minimum and if you have extra calories to place towards fats, that will be a bonus. In terms of a percentage, according to a study published in the Journal of the American Dietetic Association, it’s recommended to consume a diet that contains 20-25% of your total calorie intake from dietary fat, but going down to 15% should not prove to have any negative repercussions. So while aiming for fat loss, 15% may be a better number to target.

When choosing your fats, you’ll want to opt for sources of fats that are monounsaturated fats, especially the omega-3 fatty acids.

These come from nuts and seeds as well as avocados, and olive oil.

Try and stay away from too many saturated or trans fats. Since you are not consuming animal products, you’ll naturally avoid most saturated fats just fine, but do note that there are many trans fats in deep fried and overly processed foods that are plant-food friendly.

Keep these at bay in your diet to promote optimal health and body composition.

Putting It All Together

So there you have the facts on how calories and macronutrients interact to give you the best possible weight loss results. Also remember that whether or not you are exercising, specifically strength training, will also come into play here.

Those who engage in strength training regularly are providing a stimulus to their body, prompting the retention of lean muscle mass and this will also help them keep their metabolic rate higher and thus, allow them to see better results.

Furthermore, by engaging in exercise training, you’ll help to boost your metabolic rate even higher, as noted earlier, so this can give you an added edge.

While diet is absolutely key to fat loss, diet and exercise in combination will always yield the absolute best results.

References:

American College of Sports Medicine, and American Dietetic Association. “Joint Position Statement: nutrition and athletic performance. American College of Sports Medicine, American Dietetic Association, and Dietitians of Canada.” Medicine and Science in Sports and Exercise 32.12 (2000): 2130.